Writing instrument



FIG. 1 is a perspective view of a writing instrument;

FIG. 2 is a front elevational view of the writing instrument of FIG. 1;

FIG. 3 is an enlarged top plan view of the writing instrument of FIG. 1; and,

FIG. 4 is an enlarged bottom plan view of the writing instrument of FIG. 1.

The broken lines are included for the purpose of illustrating environment and form no part of the claimed design. 

CLAIM What is claimed is the ornamental design for a writing instrument, as shown and described. 